Epstein-Barr Virus (EBV) is the causative agent of heterophile positive infectious mononucleosis and is associated with two malignant diseases Burkitts lymphoma, a childhood cancer common in tropical Africa and nasopharyngeal carcinoma which occurs in highest incidence in Southeast Asia. The appearance of EBV-genome positive lymphomas in immunosuppressed patients is also becoming a cause for concern in this country. By adolescence 80% of the U.S.A. population is sero-positive for EBV and the virus persists in a latent state in B-lymphocytes throughout adult life. An understanding of the mechanisms controlling establishment of latency and induction of the viral lytic cycle should be of relevance to elucidating the role of EBV in these tumors and to the management of immunosuppressed patients (oncology patients, bone marrow, heart and renal transplant patients and AIDS victims) where reactivated infections are a frequent complication. The long term objectives of the project are to describe and understand the various mechanisms involved in regulating the expression of the EBV genome during maintenance of the latent state, during induction from latency and during the different temporal stages of the lytic cycle. The initial goals are 1. To identify the regulatory sequences (or polypeptides) which are responsible for the conversion from latency to the lytic cycle. The roles of the related NotI and PstI repeat genes and other elements in activation of specific early antigen and virus capsid antigen genes will be evaluated in DNA transfection and microinjection systems. In addition, the complex upstream promoter from the lytically expressed NotI repeat gene will be linked to heterologous test genes in hybrid recombinant plasmid constructions which will be used to assess whether the palindromic features contribute to its strength as a promoter and to examine its ability to respond to TPA and other inducers. 2. To use DNA transfection and microinjection assays to identify and map the genes for additional EBV antigens and to examine co-transfection with potential regulatory fragments as a means of activating expression of genes which are normally silent in this assay. 3. As a step toward identifying the specific viral genes directly involved in lymphocyte immortalization an attempt will be made to rescue recombinant transforming virus from P3HR-1 cultures by microinjection of those DNA fragments that are lacking in P3HR-1 and are implicated in the immortalization process.